Progress in EUV resists towards high-NA EUV lithography

Abstract

High-NA extreme ultraviolet lithography (EUVL) is going to deliver the high-volume manufacturing (HVM) patterning for sub-7 nm nodes for the semiconductor industry. One of the critical challenges is to develop suitable EUV resists at high resolution with high sensitivity and low line-edge roughness (LER). The resist performance is generally limited by the resolution-LER-sensitivity (RLS) tradeoff and it is critical to find new resists that have a performance beyond this tradeoff. EUV interference lithography (EUV-IL) is a powerful and efficient technique that can print high resolution: half pitch (HP) down to 6 nm nanostructures. In this work, we evaluate the performance of the EUV resists, including molecular resist, inorganic resist, chemically-amplified (CAR) and metal sensitizer chemically-amplified resist (Metal-CAR). Six resists with the best performance have been compared in dose-to-size, line-edge roughness, exposure latitude for half pitch 16 nm and 14 nm. The molecular resist A showed lowest dose to resolve HP 16 nm (35 mJ/cm2) and 14 nm (41 mJ/cm2) but with high line edge roughness (LER 3.5 nm). CAR resist C provided lowest LER 1.9 and 1.8 nm for HP 16 nm and HP 14 nm, respectively, but with higher doses 74 mJ/cm2 (HP 16 nm) and 69 mJ/cm2 (HP 14 nm). The inorganic resist showed comprehensive good performance, giving low LER of 2.1 nm with 50 mJ/cm2 and 42 mJ/cm2 for HP 16 nm and HP 14 nm, respectively. Using the simplified Z-factor model, we showed that the LER of the resists was improved over the last two years. As the inorganic resist could resolve HP 11 nm with dose 67 mJ/cm2, we conclude it to be the current best candidate to partially resolve the RLS tradeoff problem and could be the potential EUV resist for semiconductor technological node printing.